The tension with Bladesinger is that they are easily the best gish subclass, but Wizarding is so much more useful than melee that even the best gish subclass is better off Wizarding if they can.
A Bladesinger playing as a traditional controller/caster is a more powerful character than a Bladesinger playing as a dedicated melee combatant. But a Bladesinger with average or better rolls, optimized and playing as a dedicated melee combatant is better at tanking melee and more survivable in this role than an optimized Fighter, Paladin, Barbarian or any other class with the same ability scores at most levels.
When I am playing a Bladesinger the PC is usually almost entirely focused on melee tanking. I am using 3rd-7th level slots primarily for False Life, contingency-5th level False Life and occasionally Song of Defense. Low level slots for Blur, PEG, Shield, Absorb Elements and occasionally Silvery Barbs if a crit sneaks in. In that role a Bladesinger is the premier single-class melee character at most levels over 5th.
If I am playing a more traditional spell caster then I am not usually playing a Bladesinger. It is not that a Bladesinger is bad as a traditional Wizard, they are still one of the most powerful characters at most levels. But an Enchantment, Scribes, War or Divination is better at this than a bladesinger at almost every level.
That is not to say there are not ways to completely nerf a Bladesinger in melee. They are reliant on magic spells, so things like Dispel Magic and Counterspell are very effective. Dispel Magic can eliminate their concentration spell, their temp hit points, their contingency and any other spell they have affecting them in one action.